JP4728405B2 - Surface treatment equipment - Google Patents

Description

  The present invention relates to a surface treatment apparatus that performs surface treatment of a semiconductor substrate or the like.

  Conventionally, in a manufacturing process of a semiconductor device or the like, a surface processing apparatus using plasma processing such as etching, sputtering, plasma CVD, or ashing has been used. This type of surface processing apparatus is configured to generate a plasma in a vacuum vessel and to perform a predetermined process on the surface of a substrate to be processed or a wafer.

  In particular, in a surface treatment apparatus using high-frequency plasma, a high frequency is applied to an electrode via a matching circuit, and discharge starts. In a conventional apparatus, impedance matching is performed by a matching circuit to minimize a reflected wave with respect to incident power from a power source. However, this impedance matching is seen from the high frequency power source, not from the plasma as the load. For this reason, the matching in the matching circuit cannot cause resonance in the transmission system including the electrodes. However, if the high-frequency circuit including the electrodes is in a resonance state, power can be efficiently supplied to the electrodes, and the plasma density can be improved or the discharge start pressure can be lowered.

  Here, the prior art will be described by taking a sputtering apparatus as an example. Patent Document 1 discloses a so-called two-frequency capacitive coupling type sputtering apparatus that applies high-frequency power having different frequencies to upper and lower electrodes of a parallel plate. The circuit configuration and operation of this apparatus will be described with reference to FIG.

In FIG. 8, reference numeral 1001 indicates a vacuum vessel, reference numeral 1002 indicates a target, reference numeral 1003 indicates an upper electrode, reference numeral 1004 indicates a wafer, reference numeral 1005 indicates a lower electrode, and reference numeral 200 indicates a magnet for magnetizing plasma. Plasma is formed between the target 1002 and the wafer 1004. An RF power source of 13.56 MHz is connected to the upper electrode 1003 via a matching circuit, and an RF power source of 100 MHz is connected to the lower electrode 1005 via a matching circuit. A resonance circuit 104b composed of C ₅ , L, and C _S is connected between the lower electrode 1005 and the matching circuit, and the resonance frequency f _{0 of the} series resonance circuit composed of L and C _s therein. Is equal to the frequency of 13.56 MHz applied to the target 1002.

  That is,

By doing so, it is possible to prevent a high frequency of 13.56 MHz from being applied to the lower electrode (susceptor) 1005, and it is possible to perform bias sputtering of the insulating thin film without damaging the wafer.
JP 63-50025 A

  However, the following problems are recognized in the above prior art.

  In the conventional apparatus described above, the resonance circuit is configured to ground the lower electrode, so that resonance does not occur in the circuit including the electrode. If resonance occurs in a wider range, the value of current flowing in the circuit increases and the potential difference between the electrodes also increases.

  Also, when such a resonance occurs, the maximum current / minimum voltage is at the resonance node, the maximum voltage / minimum voltage at the resonance node, and the maximum voltage / minimum current at the antinode of the resonance due to the electrode position on the distributed constant circuit. The current ratio changes. In an actual apparatus, the position of the electrode and the difference in dielectric constant of the dielectric material are not completely the same for each apparatus, so that a so-called machine difference occurs and the plasma state changes for each apparatus. In addition, when the apparatus is operated, a film gradually adheres to the walls of the processing chamber, thereby changing the circuit state and changing the plasma state for each lot.

  For example, in an inductively coupled plasma generator, a voltage is generated by the impedance of the coil when a current is passed through the coil. For this reason, not only inductive coupling but also capacitive coupling occurs, not only inductive coupling efficiency is reduced, but also the insulator covering the electrode, the Si plate, and the like are etched.

  Therefore, an object of the present invention is to provide a surface treatment apparatus capable of generating resonance on a line including electrodes.

In order to achieve the above object, a surface treatment apparatus of the present invention includes a vacuum container that accommodates a substrate to be processed and can be evacuated,
An upper electrode and a lower electrode disposed opposite to each other in the vacuum vessel;
First high-frequency power supply means for supplying a first high-frequency power to the upper electrode via a first matching circuit;
Second high frequency power supply means for supplying a second high frequency power to the lower electrode via a second matching circuit;
A resonant circuit connected between the lower electrode and ground;
A processing gas supply means for supplying a processing gas into the vacuum vessel;
In a surface treatment apparatus for producing a plasma of the processing gas between the upper electrode and the lower electrode and processing the surface of the substrate,
E Bei electrode phase position adjusting means for adjusting the phase position of the electrode,
The electrode phase position adjusting means is composed of a variable capacitor or a variable inductor, and is connected to at least one of between the upper electrode and the first matching circuit and between the lower electrode and the resonance circuit. and said that you are.

  ADVANTAGE OF THE INVENTION According to this invention, the surface treatment apparatus which can generate | occur | produce resonance on the track | line containing an electrode can be provided.

It is a figure which shows the surface treatment apparatus which concerns on one Embodiment of this invention. It is the simplified circuit diagram for demonstrating a resonance state. It is a figure explaining the effective length of the electric wire in an end. It is the figure explaining the effective length of the electric wire by impedance. It is a figure which shows the flow of the electric current in an electrode part. It is a figure which shows the flow of the electric current in an electrode part. It is a figure which shows the electric current maximum and voltage maximum mode in an electrode part. It is sectional drawing of the sputtering device by a prior art.

  Hereinafter, embodiments of the film forming apparatus of the present invention will be described in detail. However, the components described in this embodiment are merely examples, and the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments. .

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a surface treatment apparatus according to an embodiment of the present invention. The surface treatment apparatus according to the embodiment shown in FIG. 1 is an etching apparatus.

  In FIG. 1, reference numeral 1 is a vacuum vessel, reference numeral 3 is an upper electrode, reference numeral 8 is an upper electrode introduction bar, reference numeral 5 is a lower electrode, reference numeral 9 is a lower electrode introduction bar, and reference numeral 4 is a process accommodated in the vacuum container 1. The wafer (substrate | substrate) to which is given is shown. Reference numeral 6 denotes an electrostatic chuck for wafer adsorption, and reference numeral 7 denotes a lower electrode shield. Further, reference numeral 50 denotes an electrical length adjusting unit made of a capacitor, an inductor, etc., reference numeral 51 denotes a pp current detector, and reference numeral 52 denotes a pp voltage detector. The upper electrode 3 and the lower electrode 5 are disposed facing each other in the vacuum vessel. The upper electrode 3 is insulated from the outer wall of the earth potential by the insulating material 10, and the lower electrode 5 is insulated from the outer wall of the earth potential by the insulating material 11. The upper electrode 3 is connected to a high frequency power supply 16 (first high frequency power supply means) in the VHF band (preferably 60 MHz) via a first matching circuit in the matching device 17. The lower electrode 5 is connected to a high frequency power source 18 (second high frequency power supply means) from the MF band to the HF band (preferably 1.6 MHz) through a second matching circuit in the matching device 19. Although not shown in the drawing, the vacuum vessel 1 is provided with an exhaust mechanism and a processing gas supply mechanism, and is also provided with a substrate transport mechanism.

  In order to operate this etching apparatus, the vacuum vessel 1 is depressurized to a predetermined pressure using a vacuum exhaust mechanism, and then a processing gas is introduced into the vacuum vessel from the lower surface of the upper electrode 3 via a gas supply mechanism (not shown). To a predetermined pressure. Thereafter, a first high-frequency power in the VHF band (preferably 60 MHz) is applied to the upper electrode 3, and a second high-frequency power in the MF band to HF band (preferably 1.6 MHz) is applied to the lower electrode 5.

  Then, relatively high density plasma and etchant are generated by the high frequency power in the VHF band applied to the upper electrode 3. The ion bombardment energy is controlled independently of the plasma density by the high frequency power from the MF band to the HF band applied to the lower electrode 5, and the intended etching process is executed. In order to increase the plasma density, the following operation is performed.

  When the input power reaches 60% of the steady operation and the plasma density becomes constant, the current voltage indicated by the Ipp detector (current measuring device) 61 and the Vpp detector (voltage measuring device) 62 of the lower electrode 5 is used. The variable capacitor 63 is adjusted so that the resonance peak is realized. Then, resonance in the lower space of the lower electrode 5 is realized. When resonating in this way, the plasma electron density between the two electrodes increases, the dissociation of the reaction gas proceeds, the dissociated radicals become dense, high selectivity, etching shape without bowing, and uniform in-plane distribution. can get.

  Next, with reference to FIG. 2, the adjustment of matching and the adjustment of resonance, which are the main parts of the present embodiment, will be described. In FIG. 2, the high-frequency power source 18 and the matching device 19 for the lower electrode 5 are omitted. The high frequency power supply 16 is connected to the upper electrode 3 through the matching device 17. The matching device 17 includes an impedance measuring device 21 that measures phase and amplitude, a plasma generation measuring device 28 that detects the generation of plasma, variable capacitors 22 and 23 that form a matching circuit, and a coil 27. . Control of the variable capacitors 22 and 23 is performed by the motor units 24 and 25. The matching controller 26 receives a signal from the plasma generation measuring device 28 and a signal from the impedance measuring device 21 and sends a command signal to the motor units 24 and 25 so that the capacitors 22 and 23 take a target value.

  The lower electrode 5 is grounded via the electrical length adjusting unit 70 and the resonance adjusting unit 60. The resonance adjustment unit 60 includes a variable inductor 67 and a variable capacitor 63 that constitute a resonance circuit, and a resonance controller 65 that sends a command signal to a motor unit 64 that drives the variable capacitor 63. The resonance adjustment unit 60 further detects a value of the peak-to-peak current and sends it to the resonance controller 65, and detects a peak-to-peak voltage value and detects the peak-to-peak voltage value. And a p-p voltage detector 62 that sends a signal to.

  The matching device 17 and the resonance adjusting unit 60 operate as follows. When high frequency power is supplied between the electrodes 3 and 5 from the high frequency power supply 16, plasma is generated. Upon detecting the generation of the plasma, the plasma generation measuring device 28 sends a signal to the matching controller 26. Further, the impedance measuring device 21 sends the detected current / voltage phase difference and the impedance value obtained from the measured voltage and current to the matching controller 26. The matching controller 26 sends signals to the motor units 25 and 24 so that the impedance value is the same as that of the high frequency power supply 16 and the current / voltage phase difference is zero. The motor units 25 and 24 rotate according to the value of this signal and adjust the values of the variable capacitors 23 and 22.

  On the other hand, the resonance adjustment unit 60 starts control of the resonance circuit when the power reaches 60% of the steady state. The pp current detector 61 sends the detected peak-to-peak current value to the resonance controller 65, and the pp voltage detector 62 sends the detected peak-to-peak voltage value to the resonance controller 65. The resonance controller 65 determines the changing direction and value of the capacitance value of the variable capacitor 63 so that the value of the voltage × current is maximized, sends a signal to the motor unit 64, and the motor unit 64 sets the variable capacitor 63 according to the instruction. Change. In the present embodiment, the resonance adjusting unit 60 is not provided with a phase measuring device. However, if the phase difference of the current voltage is detected by the phase meter and a value is sent to the resonance controller, it can be easily calculated in which direction and how much the variable capacitor 63 should be changed. It is preferable. Further, instead of the variable capacitor, the variable inductor 67 may be adjusted to resonate.

  After realizing resonance in this way, the resonance position of the electrode is adjusted by the following procedure. In order to adjust the phase position of the electrodes 5 and 3 in the resonance state, the electrical length adjustment unit 50 provided above the upper electrode 3 and the electrical length adjustment unit 70 provided below the lower electrode are used. Change the phase position of the upper and lower electrodes. The electrical length adjusters 50 and 70 each constitute electrode phase position adjusting means. Thus, when the phase position of the upper and lower electrodes changes, the ratio of the voltage and current at the upper and lower electrodes changes, and the plasma can be changed to a desired state.

  FIG. 3 is a diagram showing the phase position adjustment of the electrodes. In a distributed constant circuit in which one end is short-circuited and the electrode is in the vicinity of the center, resonance does not occur well unless the length is an integral multiple of ½ wavelength. Furthermore, in order for the vicinity of the electrode to have a current peak, the electrode needs to be positioned near the center of one wavelength. Since the variable capacitor has the effect of shortening the short circuit end (increasing the effective length), the effective length of the resonant circuit can be changed by changing the size of the capacitor. Referring to 30b of FIG. 3, the “actual transmission line length” from the variable capacitor position B to the variable capacitor position C is longer than the resonant circuit length of one wavelength. Even in this case, by changing the value of the capacitor appropriately, the apparent resonance circuit length can be set to the “apparent transmission line length” to the resonance ends E and D which are the same as one wavelength. .

  Further, when such a variable capacitor is used, the electrode position A shown by 30a in FIG. 3 can be arranged at the current peak position by adjusting the balance between the upper and lower capacitor values. The same adjustment can be made by changing the inductor instead of the capacitor. If one of the resonance circuits is open and the other is short-circuited, resonance can be caused at half wavelength.

  In the present embodiment, the resonance adjustment unit 60 and the electrical length adjustment unit 70 are provided on the lower electrode, but either one may be omitted. For example, when the electrical length adjustment unit 70 is omitted, the remaining resonance adjustment unit 60 plays both roles of resonance and electrical length adjustment. This simplifies the apparatus and reduces the cost, and furthermore, since the resonance adjustment and the electrical length adjustment are performed at the same place, the adjustment can be performed quickly.

  The concept that is the basis of the adjustment of the effective line length of resonance and the adjustment method of the electrode position will be described using equations.

L is the inductance per unit length of both wires, C is the capacitance per unit length between both wires, R is the reciprocal conductor resistance per unit length of both wires, and S is the unit length between both wires Of leakage conductance. In point on lead at a distance y becomes measure from left power supply side, the potential difference between the E _y both lines, if the current on the conductive wire I _y, the following equation is obtained.

-DEy / dy = (R + jωL) · Iy = Z · Iy
-DIy / dy = (S + jωC) · Ey = Y · Ey
Solving this equation gives the following equation:

If the potential and current at the power transmission end, that is, y = 0, are E _s and I _s , the following equation (1) is obtained.

Next, when the voltage and current at the power receiving end, that is, y = l are E _r and I _r , the following equation (2) is obtained.

In the case of a receiving end short circuit, E _r = 0. Therefore, the following formula is obtained from the formula (2).

  However, lossless R = 0, S = 0,

  Substituting this into equation (2) yields the following equation (3).

  When l−y = x is used for Equation (3), which is impedance when the y point is viewed from the right, the transmission end impedance Zx obtains the following pure reactance.

  Thus, if the length is x = λ / 2, the system is in series resonance.

When this system is terminated at L, based on the relationship of E _r = jωL · I _r , assuming that the conducting wire is lossless and l is x, the impedance of the power transmission end: Z _x is obtained.

  here,

This means that have the same characteristics as the only long short resonant line x _L, it is equivalent to a short circuit resonance line extended by x _L.

Further, when this system is terminated at C, based on the relationship of E _r = I _r / jωC, assuming that the conducting wire is lossless and l is assumed to be x, the impedance: Z _x of the power transmission end is obtained.

This means that have the same characteristics as a short short resonant line x _L, is equivalent to a short circuit resonance line was shortened by x _L.

  This change in the line length is expressed by Equation (4) or Equation (5). This is illustrated in FIG. Changes in the effective distance when terminated with L or C are determined by the size of the terminating capacitance or inductance, the characteristic impedance of the line, and the power supply frequency. For this reason, for example, when the variable capacitor 73 on the lower electrode 5 side is changed, the effective line length is changed and the phase position of the electrode is changed. In order to cancel the change in the line length and maintain the resonance, it is only necessary to change the variable capacitor 53 on the upper electrode 3 side in the opposite direction by the same amount. However, since the characteristic impedance of the line actually differs depending on the location, it is necessary to change it so that the equation is satisfied in consideration of this. Although the rough change guideline can be calculated in this way, there are actually some things that cannot be calculated, such as changes in the plasma state. For this reason, even if a rough adjustment is performed based on the calculated value, the current / voltage state is monitored so as to satisfy the resonance for fine adjustment, and the electrode position is adjusted to the target current / voltage while adjusting the circuit state accordingly. It is necessary to keep it in a state.

  The actual adjustment is performed as follows, but there are many similarities to the adjustment of the matching circuit and the resonance circuit, and only the concept is shown. The difference in phase distance between the Ipp detector 71 and the Vpp detector 72 and the phase distance to the upper and lower electrodes 3 and 5 are calculated in advance, and the phase distance is confirmed by measurement. The variable capacitor 73 and the variable inductor 77 are set so that the ratio of Vpp (voltage) and Ipp (current) at the upper and lower electrodes 3 and 5 becomes a preset desirable value from the values measured by the Ipp detector 71 and Vpp detector 72. To change. In response to this change, the variable capacitor 53 and the variable inductor 77 on the upper electrode side are changed, and the resonance adjustment unit 60 is also changed if necessary.

  Next, using FIG. 5, FIG. 6, and FIG. 1, a resonance adjustment unit and an electrical length adjustment unit for a resonance circuit may be provided on either the upper electrode 3 side or the lower electrode 5 side, which should be noted in the device structure. Explain that it doesn't matter. In the figure, reference numeral 8 denotes an upper electrode conductive rod, and a high-frequency conductive current 8a flows through this surface. Further, the conductive current 8a flows on the surface of the upper electrode 3 as the upper electrode external current 3a, and further flows on the surface of the upper electrode 3 as the upper electrode plasma side current 12b. Since this current has no place to go, charges accumulate on the electrode surface, and an upper sheath current 12a indicating the sum of displacement current, ion current, and electron current flows through the upper sheath 12 in accordance with the electric field induced by this charge. The plasma 15 has the same potential, and a plasma current 15a, which is a conductive current corresponding to the upper sheath current 12a, flows to generate an electric field in the lower electrode sheath 13 on the opposite side of the electrode, and a displacement current and an ion corresponding to the electric field are generated. A lower sheath current 13a, which is the sum of current and electron current, flows. Due to this current and voltage, a lower electrode plasma side current 13b flows on the surface of the lower electrode 5, and further flows out as a lower electrode external current 5a and an introduction rod current 9a. From the current conservation law, the upper sheath current 12a and the lower sheath current 13a have the same current value. This constant current value is maintained even in a specific symmetry electric field in which one of the electrodes is grounded. Therefore, it does not matter whether the resonance circuit is provided on the upper electrode side or the resonance circuit on the lower electrode side as long as the upper and lower electrodes are included in the resonance circuit.

  However, in reality, this current is not such, and a part of the current escapes to other than the electrodes as shown in FIG. That is, a part of the upper electrode external current 3a escapes from the upper electrode shield 7a serving as an external conductor to the ground as currents 7c1 and 7b1, and the value of the upper electrode external current 3a is larger than the value of the lower electrode external current 5a. In the lower electrode, part of the lower electrode external current 5a escapes to the lower electrode shield 7, so that the introduction rod current 9a flowing on the surface of the lower electrode introduction rod 9 is further reduced. However, when the resonance state is reached, the impedance of the resonance line approaches zero, and the amount of current that escapes to the parasitic capacitance is reduced.

  However, the current escaping to the parasitic capacitance, that is, the apparent power, reduces the magnitude of the current and voltage applied to the electrode accordingly. For this reason, it is preferable to reduce the capacitance by widening the gap between the electrode and the shield so that the parasitic capacitance of the upper electrode shield 7a and the lower electrode shield 7 is reduced and reducing the opposing area.

  When the resonance state is realized, the impedance at the electrode is lowered and the power is reflected at the resonance end. On the other hand, since the current flows into the resonance part without being reflected by the matching circuit, the current is accumulated in the resonance part, and the power is efficiently consumed by the plasma between the upper and lower electrodes placed in the resonance part.

  Next, the state of the maximum current and maximum voltage modes will be described.

  Reference numeral 70a in FIG. 7 denotes the maximum current mode. In the maximum current mode, A1 indicating the potential difference between the electrode and the shield and the potential difference A3 between the thin plasma near the shield and the electrode should be almost negligible values. If no current is accumulated, the voltage A2 between the electrodes should be small. However, in reality, not much current flows between the plasma and the upper electrode, and between the plasma and the lower electrode, most of which becomes a displacement current, and electric charges accumulate on the electrode and the surface of the plasma, generating a large voltage.

  On the other hand, a displacement current hardly flows in the plasma and a large conduction current flows, and ionization occurs efficiently. A part of the current flows into the plasma as an actual current, but the remaining current flows from the outer periphery to the inner periphery of the electrode, so that a potential difference is generated between the electrode periphery and the electrode center by the phase difference of the electrode length. When the electrode center has the maximum current and the minimum voltage, the difference between the electrode potential and the plasma potential increases toward the outer periphery, and a larger plasma generation density is obtained at the electrode outer periphery than at the electrode center, thus compensating for the plasma lost by diffusion. For this reason, it is easy to obtain a more uniform plasma density. However, there is also a phenomenon in which a current transmitted as a wave is concentrated at the center of the electrode, and the plasma density becomes deep at the center. When uniform plasma cannot be obtained in this way, the voltage ratio may be increased as described later.

  Here, the potential difference A2 between the shield and the electrode and the potential difference A3 between the shield and the plasma in the vicinity of the shield change as the potential difference A2 between the electrodes increases, and the accompanying effects are considered.

  When the electrode center is at a phase position of zero voltage, the voltage at the upper electrode and the voltage at the lower electrode have the same absolute value and opposite signs. The plasma is not at a lower potential than the electrodes, and the plasma potential will fluctuate between half the potential difference between the electrodes, that is, between zero and the peak potential. At this time, plasma generation does not occur at an electrode having the same potential as plasma, but an electrode having the same potential as the peak-to-peak potential is generated at an electrode having a potential opposite to that of plasma, and a large amount of plasma is generated.

  On the other hand, the potential difference between the outer peripheral plasma and the electrode is consumed by the sheath of the electrode portion, and does not contribute to the generation of the outer peripheral plasma. Further, when the potential difference between the upper electrode 3 and the lower electrode 5 increases, the potential difference between the upper and lower electrodes and the shields 7 and 7a constituting the external conductor also increases. However, since there is an insulator between the shield and the electrode, the shield No plasma is generated even if the potential difference A1 between the electrode and the electrode increases.

  However, the potential difference A3 between the outer peripheral plasma and the shield, which varies by half the potential difference between the electrodes, becomes a problem. If the shield is fully grounded, the potential of the shield is zero. As already discussed, the potential of the peripheral plasma fluctuates by half the value of the peak-to-peak potential at the electrode, and the potential difference between the shield and the peripheral plasma is half of the potential difference between the electrode and the plasma. Even if not, plasma is generated. However, if the plasma is sufficiently attenuated and the plasma is extinguished at the shield part, such a potential difference is not produced, but the method of this embodiment alone cannot sufficiently attenuate the plasma at the outer peripheral part, and the plasma is not generated. It cannot be suppressed. Therefore, another method is required.

  Reference numeral 70b in FIG. 7 denotes a voltage maximum mode. In this case, the electrode voltage fluctuates greatly, but this voltage is applied to the voltage B1 or B3 between the electrode and the shield, and plasma is generated between the outer peripheral plasma and the shield that fluctuates by half of the peak-to-peak potential. To do. In contrast, the voltage indicated by B2 should be almost zero. However, in actuality, since the plasma cannot be higher than the potential of the contacted portion, a potential difference that is half the peak-to-peak potential is applied between the plasma and the electrode. Actually, the current and voltage that are 180 ° out of phase with the inner conductor (electrode) flow through the outer conductor (shield), so this consideration is not sufficient, but it is qualitatively the same.

  If the inner conductor (electrode) and the outer conductor (shield) are separated sufficiently, the increase in the voltage of the inner conductor in the maximum current mode has little influence on the outer conductor. The problem is that the voltage generated between the electrodes in the maximum current mode generates a current corresponding to the voltage. This can be considered as follows. If an inductor having the same absolute value of impedance as the electrode and an opposite polarity is connected near the electrode, the voltage generated by the inductor is canceled with the voltage generated by the electrode. Although it is desirable to do this, even without this, the electrical length adjusting unit 70 of FIG. 2 can perform the same function, and can cancel the voltage generated at the electrode and perform an unrivaled function.

  The above is summarized as follows. In the current maximum mode, plasma at the electrode is generated based on the peak-to-peak potential, and is generated at a half of the peak-to-peak potential in the periphery. On the other hand, in the maximum voltage mode, plasma is generated at half of the peak-to-peak potential in both the electrode portion and the peripheral portion. As the voltage ratio is increased in this way, the plasma density in the outer peripheral portion increases and the plasma density decreases in the central portion as compared with the maximum current mode. Thus, the uniformity of the plasma density can be changed by changing the ratio of the current and voltage in the resonance state, that is, the position of the electrode on the resonance circuit.

  If the distribution cannot be obtained in the maximum current mode, the current / voltage ratio becomes about 3/1 when the electrode is shifted by ± 1/20 wavelength from the phase position in the maximum current mode, which is the phase position regarded as the short-circuited end. The in-plane distribution of ± 15% improves to ± 4%.

  When the lower electrode 5 is set to fall to the ground with respect to the power supply frequency of the upper electrode 3, that is, when the lower electrode 5 serves as an outer conductor, the upper electrode is contrary to the above description. 3 requires the voltage maximum mode. However, in this case, the maximum voltage can be achieved automatically because the upper electrode is open at resonance. Actually, it does not become a perfect outer conductor, and some elements of the capacitor are included. For this reason, there is room for adjustment to the maximum voltage. Although this can be realized by the above explanation, a detailed explanation is omitted.

  If the distribution cannot be obtained in the maximum voltage mode, the current / voltage ratio becomes about 1/3 when the electrode is shifted by ± 1/20 wavelength from the phase position in the maximum voltage mode, which is the phase position regarded as a short-circuited end, and the first etching is performed. The in-plane distribution of ± 10% improves to ± 4%.

  As described above, in this embodiment, the phase position is adjusted by providing a variable capacitor and a variable inductor. However, by calculating or experimenting, the electric circuit length of the device is set so as to optimize the phase position of the electrode, and the resonance is achieved. You may let them. In this case, if FIG. 1 is taken as an example, the electrical length adjusting units 50 and 70 that cause resonance are unnecessary, and it is possible to omit the capacitors and inductors at those portions or to use fixed capacitors and inductors. Become. In addition, since the electrode is brought to a desired resonance phase position, the length of the electrode rod can be designed to a desired value.

  In addition, for simplicity of explanation, resonance occurred between the matching circuit and the ground, but considering the circuit length in all paths from the matching circuit to the matching circuit via the electrodes and the electrical length adjuster, It is more preferable to consider the resonance there.

  As described above, according to the present embodiment, it is possible to determine which position of the phase in the resonance the electrode occupies in the resonance state. For example, the current value can be increased or the voltage value can be increased. Further, by selecting the phase position, not only the reproducibility of the plasma processing can be improved, but also a plasma state such as a high plasma density can be determined.

  Thus, according to the present embodiment, it is possible to provide an easy-to-use and reliable plasma surface treatment apparatus that can control the plasma state with high accuracy.

  Of course, the above-described method can be used for starting and maintaining discharge at a low gas pressure. Since the voltage between the electrodes becomes high, the discharge can be easily started even at a low pressure where the discharge is difficult to start. For this reason, for example, when performing an etching process, there is an effect that an oblique incident amount of ions is reduced and a desirable etching shape without bowing can be obtained even in a contact hole having a high aspect ratio. Further, since the plasma density is increased, contact holes having a high aspect ratio can be etched at a high selectivity.

  In the present embodiment, the plasma apparatus in general has been described as an example. However, it is obvious that this embodiment can be applied to an etching apparatus using plasma, sputtering, plasma CVD, ashing, surface oxidation, nitridation, a surface modification apparatus for removing compounds such as surface oxides, and the like.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and various modifications can be made within the technical scope grasped from the description of the scope of claims. Is possible.

  The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

  This application claims priority based on Japanese Patent Application No. 2007-176287 filed on Jul. 4, 2007, the entire contents of which are incorporated herein by reference.

Claims (4)

A vacuum container that accommodates a substrate to be processed and can be evacuated;
An upper electrode and a lower electrode disposed opposite to each other in the vacuum vessel;
First high-frequency power supply means for supplying a first high-frequency power to the upper electrode via a first matching circuit;
Second high frequency power supply means for supplying a second high frequency power to the lower electrode via a second matching circuit;
A resonant circuit connected between the lower electrode and ground;
A processing gas supply means for supplying a processing gas into the vacuum vessel;
In a surface treatment apparatus for producing a plasma of the processing gas between the upper electrode and the lower electrode and processing the surface of the substrate,
E Bei electrode phase position adjusting means for adjusting the phase position of the electrode,
The electrode phase position adjusting means is composed of a variable capacitor or a variable inductor, and is connected to at least one of between the upper electrode and the first matching circuit and between the lower electrode and the resonance circuit. surface treatment apparatus characterized by there.   The electrode phase position adjusting means is arranged so that the electrodes are arranged at the phase position where the voltage is maximum and the current is minimum at the electrode, or at the phase position where the voltage is minimum and the current is maximum at the electrode. The surface treatment apparatus according to claim 1, wherein a phase position of the electrode is adjusted. A vacuum container that accommodates a substrate to be processed and can be evacuated;
An upper electrode and a lower electrode disposed opposite to each other in the vacuum vessel;
First high-frequency power supply means for supplying a first high-frequency power to the upper electrode via a first matching circuit;
Second high frequency power supply means for supplying a second high frequency power to the lower electrode via a second matching circuit;
A resonant circuit connected between the lower electrode and ground;
A processing gas supply means for supplying a processing gas into the vacuum vessel;
In a surface treatment apparatus for producing a plasma of the processing gas between the upper electrode and the lower electrode and processing the surface of the substrate,
The upper electrode is arranged at a position shifted by ± 1/20 wavelength of the first high-frequency power from a phase position regarded as a short-circuit end,
The surface treatment apparatus, wherein the lower electrode is arranged at a position shifted by ± 1/20 wavelength of the second high-frequency power from a phase position regarded as a short-circuit end. The resonant circuit of the surface treatment apparatus according to claim 1 or 3, characterized in that it contains a voltage measuring device and a current measuring device.

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